Electron emission device with specific island-like regions

Abstract

An electron emission device includes an electron-supply layer formed of metal or semiconductor; an insulator layer formed on the electron-supply layer; and a thin-film metal electrode formed on the insulator layer, whereby electrons are emitted when an electric field is applied between the electron-supply layer and the thin-film metal electrode. The insulator layer and the thin-film metal electrode have at least one island-like region where the thicknesses of the insulator layer and the thin-film metal electrode gradually decrease.

What is claimed is:  
     
       1. An electron emission device comprising: 
       an electron-supply layer made of a semiconductor material, a metal compound or metal;  
       an insulator layer formed on the electron-supply layer; and  
       a thin-film metal electrode formed on the insulator layer,  
       characterized in that the insulator layer and the thin-film metal have a plurality of island-like regions where thicknesses of both the insulator layer and the thin-film metal electrode gradually decrease.  
     
     
       2. An electron emission device according to claim  1 , wherein said island-like regions are electron emission sites. 
     
     
       3. An electron emission device according to claim  1 , wherein said insulator layer is made of dielectric and has a film thickness of 50 nm or greater. 
     
     
       4. An electron emission device according to claim  1 , wherein the thin-film metal electrode is terminated on the insulator layer in each of the island-like regions. 
     
     
       5. An electron emission device according to claim  1 , wherein the insulator layer is terminated on the electron-supply layer in each of the island-like regions. 
     
     
       6. An electron emission device according to claim  1 , wherein each of the island-like regions is a recess formed in a flat surface of the thin-film metal electrode. 
     
     
       7. An electron emission device according to claim  1 , wherein the insulator layer and the thin-film metal are formed by a physical vapor deposition and/or chemical vapor deposition. 
     
     
       8. An electron emission device according to claim  1 , wherein a minute particle is provided in each of the island-like regions. 
     
     
       9. An electron emission device according to claim  1 , wherein an inverse tapered block is provided in each of the island-like regions. 
     
     
       10. A method of manufacturing an electron emission device having a plurality of island-like regions where thicknesses of an insulator layer and a thin-film metal electrode gradually decrease, said method comprising the steps of: 
       forming an electron-supply layer on a substrate;  
       spraying a plurality of minute particles onto the electron-supply layer;  
       depositing an insulator material on the electron-supply layer and the minute particles, thereby forming a thin insulator layer; and  
       forming a thin-film metal electrode on the insulator layer and the minute particles, thereby forming island-like regions around a contact surface under the minute particles.  
     
     
       11. A method according to claim  10  further comprising a step of applying a voltage across the electron-supply layer and the thin-film metal electrode for growth of conductive paths after the thin-metal electrode forming step. 
     
     
       12. A method according to claim  10  further comprising a step of removing the minute particles from the island-like regions after the thin-metal electrode forming step. 
     
     
       13. A method according to claim  12  further comprising a step of applying a voltage across the electron-supply layer and the thin-film metal electrode for growth of conductive paths after the minute particle removing step. 
     
     
       14. A method of manufacturing an electron emission device having a plurality of island-like regions where thicknesses of an insulator layer and a thin-film metal electrode gradually decrease, said method comprising the steps of: 
       forming an electron-supply layer on a substrate;  
       forming electrically insulative inverse tapered blocks each protruding in a direction normal to the substrate and each having an overhang portion, at an upper portion thereof, protruding in a direction parallel to the substrate;  
       depositing an insulator on the electron-supply layer, thereby forming a thin insulator layer; and  
       forming a thin-film metal electrode on the insulator layer, thereby forming island-like regions around a contact surface under the inverse tapered blocks.  
     
     
       15. A method according to claim  14  further comprising a step of applying a voltage across the electron-supply layer and the thin-film metal electrode for growth of conductive paths after the thin-metal electrode forming step. 
     
     
       16. A method according to claim  14  further comprising a lift-off step of removing the inverse tapered blocks from the island-like regions after the thin-metal electrode forming step. 
     
     
       17. A method according to claim  16  further comprising a step of applying a voltage across the electron-supply layer and the thin-film metal electrode for growth of conductive paths after the lift-off step. 
     
     
       18. A method according to claim  14 , wherein said block forming step includes steps of forming an inverse tapered block material layer on said substrate, forming a resist mask on said inverse tapered block material layer by photolithography for exposing part of at least said electron-supply layer, and carving said inverse tapered blocks having said overhang portions by dry etching or wet etching. 
     
     
       19. An electron emission display device comprising: 
       a pair of a first substrate and an optically transparent second substrate opposing to each other with a vacuum space interposed therebetween;  
       a plurality of electron emission devices formed on said first substrate, each of which including an electron-supply layer made of a semiconductor material, a metal compound or metal formed on ohmic electrodes formed on said first substrate, an insulator layer formed on said electron-supply layer, and a thin-film metal electrode formed on said insulator layer and facing the vacuum space, wherein the insulator layer and the thin-film metal have a plurality of island-like regions where thicknesses of both the insulator layer and the thin-film metal electrode gradually decrease;  
       a collector electrode formed on said second substrate; and  
       a fluorescent material layer formed on said collector electrode and facing the vacuum space.  
     
     
       20. An electron emission display device according to claim  19 , wherein said insulator layer is made of dielectric and has a film thickness of 50 nm or greater. 
     
     
       21. An electron emission display device according to claim  19 , wherein the thin-film metal electrode is terminated on the insulator layer in each of the island-like regions. 
     
     
       22. An electron emission display device according to claim  19 , wherein the insulator layer is terminated on the electron-supply layer in each of the island-like regions. 
     
     
       23. An electron emission display device according to claim  19 , wherein each of the island-like regions is a recess formed in a flat surface of the thin-film metal electrode. 
     
     
       24. An electron emission display device according to claim  19 , wherein the insulator layer and the thin-film metal are formed by a physical vapor deposition and/or chemical vapor deposition. 
     
     
       25. An electron emission display device according to claim  19 , wherein the display device further comprises plural insulative support members formed on said first substrate and disposed between adjacent ones of said electron emission devices so as to enclose the electron emission devices for partitioning them, wherein the distance from said first substrate to the surfaces of said insulative support members proximate to said vacuum space is substantially equal to the distance from said first substrate to the surface of said thin-film metal electrodes proximate to said vacuum space. 
     
     
       26. An electron emission display device according to claim  19 , wherein the display device further comprises a plurality of bus electrodes, each of which is arranged in a stripe form to electrically connect adjacent ones of said thin-film metal electrodes, wherein said ohmic electrodes and said electrodes are stripe-like electrodes and arranged to extend perpendicular to each other. 
     
     
       27. An electron emission display device according to claim  19 , wherein said first substrate includes a plurality of first insulative ramparts, each of which disposed between said electron emission devices and protruding into said vacuum space, whereas said second substrate includes a plurality of second ramparts each of which protrudes into said vacuum space to abut to said first ramparts.